puborectalis

Puborectalis is a component of the pelvic floor’s levator ani muscle group. It originates from the posterior aspect of the pubic bones on each side and encircles the lower rectum as a U-shaped sling, bridging behind the anorectal junction. The fibers interdigitate with surrounding pelvic floor muscles, contributing to the support of the rectum and the anal canal.

The primary function of puborectalis is to maintain the anorectal angle at rest. By forming a kink at the rectoanal junction, it helps preserve continence. The resting angle is typically about 80 degrees. During defecation, the puborectalis relaxes, allowing the angle to straighten and the rectum to align with the anal canal, thereby facilitating stool passage. Coordinated relaxation of this muscle, together with other pelvic floor muscles, is essential for normal defecation.

Innervation of the puborectalis mainly derives from the inferior rectal nerves, branches of the pudendal nerve, with additional input from sacral nerves as part of the pelvic floor motor supply. Dysfunction can contribute to pelvic floor disorders, including fecal incontinence or obstructed defecation due to paradoxical contraction (dyssynergia) of the muscle during attempts to defecate.

Clinical relevance includes assessment by digital rectal examination, anorectal manometry, and imaging studies such as defecography or MRI to evaluate the puborectalis sling. Management of related disorders often involves pelvic floor physical therapy and biofeedback; surgical options are uncommon and reserved for select conditions.